chriseenorjzz is mistaken thinking that "Gatefold cover" refers to an artist, a gatefold cover is an album cover that opens up, nothing more, nothing less. From Wikipedia: A gatefold cover or gatefold LP is a form of packaging for LP records which became popular in the mid-1960s. A gatefold cover, when folded, is the same size as a standard LP cover (i.e. a 12 inch, or 32.7 centimeter, square). The larger gatefold cover provided a means of including artwork, liner notes, and/or song lyrics which would otherwise not have fit on a standard record cover. It became famous as an extension of Progressive rock, as the expansive, transient gatefolds by Roger Dean or H. R. Giger became associated with concept albums. Gatefold sleeves were also used when an album contained more than one record; for example, a double album would include one record in each half of the cover.
The cover work of the Monster album by Steppenwolf was done by Gatefold. He made cover design with artwork and photos on the inside cover pages. The album was Steppenwolf's most political one, making references to important issues at the time such as the Vietnam War. Read more from vinylrecords.ch/S/ST/STE/Steppenwolf/monster/steppenwolf-monster.html.
the art work to steppenwolf`s previous album, "at your birthday party" had been done by san francisco artist rick griffin. judging by the fact that the lettering used on the sleeve of monster is very similar to that used by griffin for quicksilver albums, there is a fairly high probability that, indeed, rick griffin is the artist who did the lettering and the hr giger-like "monster" psychedelic drawing.